The exemplary embodiments relates to a method of assigning an identifier to a cell.
The speed and capacity of communication between servers and backplane boards are increasing today. Accordingly, there is a possibility that the radio environment changes after assigning a PCI (Physical Cell Identifier), which is one type of a cell identifier. Therefore, in PCI assignment, it is necessary to select a PCI that can maintain collision-free and confusion-free even when the radio environment changes.
However, enormous work is required to measure the actual radio environment. Further, detailed information elements such as obstacles are required to estimate the radio environment, and it is difficult to manage such enormous information. Therefore, there is a demand for a communication system in which a PCI that is likely to maintain collision-free and confusion-free can be assigned.
Techniques related to PCT assignment are described in Japanese Unexamined Patent Application Publication No. 2011-004377, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2010-537479, and Japanese Unexamined Patent Application Publication No. 2010-268463.
According to the handover method disclosed in Japanese Unexamined Patent Application Publication No. 2011-004377, a reconnection procedure is executed in the event PCI confusion occurs.
Further, according to the conflict resolution method disclosed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2010-537479, when a detection node detects that a first cell identifier related to a first conflict cell is the same as a second cell identifier related to a second conflict cell, one of the first and second conflict cells is selected. Then, a different cell identifier is determined for the selected cell.
However, both of the above techniques detect the overlap of an identifier such as a PCI between adjacent cells and then resolve the detected overlap of an identifier. Therefore, it is unable in PCI assignment to select a PCI that can maintain collision-free and confusion-free even when radio environment changes.
A technique related to selection of a PCI in consideration of maintaining collision-free and confusion-free is disclosed in Japanese Unexamined Patent Application Publication No. 2010-268463, for example.
According to the PCI assignment method disclosed in Japanese Unexamined Patent Application Publication No. 2010-268463, a SON (Self-Organizing Network) functional node pieces together information of an adjacent cells reported from each base station under the control thereof. Then, the SON functional node then assigns a PCI to a cell based on the adjacent cell information.
However, in this technique, only identifier information of adjacent cells of a cell formed by a base station connected to the SON functional node is transmitted to the SON functional node. This causes a problem that, when assigning an identifier such as a PCI, the SON functional node can consider the identifier information of adjacent cells of the cell formed by the base station connected to itself but cannot consider the identifier information of cells adjacent to those adjacent cells. As a result, a serious problem occurs that it is difficult to maintain collision-free and confusion-free in the event radio environment changes.
This problem is caused by the fact that there is no way for the SON functional node to know the identifier information of adjacent cells of a cell formed by a base station that is not connected to the SON functional node.
In view of the above problem, an exemplary object of the invention is to provide a communication system in which an identifier assignment device can know identifier information of adjacent cells of a cell formed by a base station that is not connected to the identifier assignment device.
However, exemplary embodiments are not required to achieve here, objectives described above, and an exemplary embodiment may not achieve any of the objectives described above.
In an exemplary aspect of the invention, a communication system includes a first base station that forms a first cell, a second base station that forms a second cell, and an identifier assignment device that assigns an identifier for identifying the second cell, wherein the first base station transmits first adjacent cell information containing identifier information of adjacent cells of the first cell to the second base station, and the second base station transmits the first adjacent cell information received from the first base station to the identifier assignment device.
In an exemplary aspect of the invention, an identifier assignment device in a communication system including a first base station forming a first cell and a second base station forming a second cell, the identifier assignment device assigning an identifier of the second cell, includes a receiving unit that receives first adjacent cell information containing identifier information of adjacent cells of the first cell from the second base station, and an identifier assignment unit that assigns an identifier of the second cell based on the first adjacent cell information received by the receiving unit.
In an exemplary aspect of the invention, a base station in a communication system including a first cell, a second cell, and an identifier assignment device that assigns an identifier of the second cell, the base station forming the second cell, includes a receiving unit that receives first adjacent cell information containing identifier information of adjacent cells of the first cell from another base station forming the first cell, and a transmitting unit that transmits the first adjacent cell information to the identifier assignment device.
In an exemplary aspect of the invention, an identifier assignment method includes a step of transmitting first adjacent cell information containing identifier information of adjacent cells of a first cell formed by a first base station to a second base station that forms a second cell, and a step of transmitting the first adjacent cell information received by the second base station to an identifier assignment device that assigns an identifier of the second cell.
In an exemplary aspect of the invention, a method for an identifier assignment device in a communication system including a first base station forming a first cell and a second base station forming a second cell, the identifier assignment device assigning an identifier of the second cell, includes a receiving step of receiving first adjacent cell information containing identifier information of adjacent cells of the first cell from the second base station, and an identifier assignment step of assigning an identifier of the second cell based on the first adjacent cell information received in the receiving step.
In an exemplary aspect of the invention, a method for a base station in a communication system including a first cell, a second cell, and an identifier assignment device that assigns an identifier of the second cell, the base station forming the second cell, includes a receiving step of receiving first adjacent cell information containing identifier information of adjacent cells of the first cell from another base station forming the first cell, and a transmitting step of transmitting the first adjacent cell information to the identifier assignment device.
In an exemplary aspect of the invention, a non-transitory computer readable medium stores a program causing a computer to execute a step of transmitting first adjacent cell information containing identifier information of adjacent cells of a first cell formed by a first base station to a second base station that forms a second cell, and a step of transmitting the first adjacent cell information received by the second base station to an identifier assignment device that assigns an identifier of the second cell.
The above and other objects, features and advantages of the present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.